Unformatted text preview: Chapter 2a: The cell — chemical and macromolecule structure. There are 10 multiple
choice questions assigned to this module. modem-M us...—
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mmsnmmwmum Opening screen: In the previous learning module we
discussed the basic functioning unit of the body - the cell.
Cells require nutrients for energy and for synthesizing the
molecules for survival. They generate waste products and
eliminate them. In this module we will discuss the general
characteristics of the four major classes of biomolecules. :__m leculesare ' b livin or ani tain carbon atoms. Click the chemical bonds button: This module is
a basic review of biochemistry. Understanding biology
requires understanding some chemistry- especially the
structure and interactions of atoms, ions, and molecules.
So the next few slides will review the chemical bonds that
hold atoms together to form the molecules required for
life. Atoms are the fundamental units and are made up of
three types of elementary particles — protons, elections
and neurons. Atoms are most stable when all of their
orbitals are occupied by Wm. Isolated atoms,
such as hydrogen (H), carbon (C), nitrogen (N) and
oxygen (0), have some orbitals that are not occupied by
8 two electrons. For example, hydrogen is an atom that has Go to next screen: Most substances are composed
of two or more atoms linked or bonded together to form
molecules. Water, for example. contains two hydrogen m bond- valsm W m m.
m M W, WWW atoms and one oxygen (1le). Most often, the atoms are
0-— mm. held together by covalent bonds, which consist of pairs
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40mm of electrons s~h_ar£d between adjacent atoms. However,
to m... “m °""'""‘°°""‘ this sharing may or may not be equal. When some
E m PM mm atoms bond with other atoms they have the tendency to
E m m 5:... pull electrons away from other atoms. These are called
I _ polar covalent bonds. When there is an equal sharing of
a m ” electrons these bonds are called nonpolar covalent
E _ - ‘ " bonds.
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m "I. Go to next screen: Oxygen and hydrogen have
em m different affinities for electrons. The nucleus of oxygen has
W a 111ch for electrons than does the nucleus
8:“. mu' mmrm ml. of hydrogen. This differential afﬁnity for electrons is seen
own-u M... hm...,,..,.....,. when a covalent bond forms between an oxygen and a w“.
56vaun hydrogen atom, Since the oxygen has a higher affinity for
electrons than does the hydrogen, the electrons in the
covalent bond between the two atoms spend a greater
fraction of their time close to the oxygen atom. The
positive charge of the hydrogen nucleus results in a partial
6 positive charge (6+). Since the electron spends a greater
ﬁacﬁon of time associated with the oxygen atom, there is a partial negative charge (6-) associated with the oxygen atom. 0; has SW, mﬁ'ﬁwﬁr eiQdo/wxs 1
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- Spring '07